The present invention concerns a hydraulic or pneumatic oscillating piston motor which has a housing, a driven shaft mounted in the housing with freedom to rotate and an oscillating piston that is rigidly attached to the shaft without freedom to rotate and that is designed as a lever with two arms having pressure areas of different size, which arms are sealed with respect to the housing. The piston divides the housing into two working spaces into which a pressure medium can be introduced and which are delimited by the two arms of the oscillating piston which maintain the seal when they move. The oscillating piston, actuated by a pressure medium, is free to oscillate back and forth through a maximum angle of rotation which is determined by means of a stop. The housing consists of a receptacle which surrounds the periphery of the shaft and which has no joints in the working space of the oscillating piston, and a cover that closes the receptacle.
An oscillating piston motor is described in German OS (laid open patent application) No. 23 09 959. In that case the maximum angle of rotation of the oscillating piston is approximately 90.degree.. Larger angles of rotation are not possible, since, due to the design, the sealing effect decreases or is eliminated when the 90.degree. mark is exceeded. The housing of the known oscillating piston motor has a wall with a contour consisting of essentially two circular sectors.
The front face of one of the arms of the lever can be moved along the circular arc surface of the first sector and is sealed off from this arc. The second, smaller arm of the lever is associated with the second sector and its sealed-off front face can likewise be displaced along the second circular arc. Both circular sectors have an aperture angle of approximately 90.degree., which establishes the maximum angle of rotation.
In order to limit the amplitude of the angle of rotation, a fixed stop is formed on one of the lever arms, which makes it impossible to arbitrarily preset a variable range for the angle of rotation.